Grinding and classifying apparatus



April 4, 1939. v R|TE$ 2,152,876

' GRINDING ANDCLASSIFYING APPARATUS" Y Filed Jan. 18, 1957 2 Sheet-Sheet1 P1 12w we;

1' lr ukenfan p i 4, 1939- J. CRITES I 2,152,876

GRINDING AND CLASSIFYING APPARATUS Filed Jan. 18, 1957 2 Sheets-Sheet 2V Patented Apr. 4, 1 939 N om n srAi-rrsrA-TENT men w iif tlmmw.

Engineering Company, Inc., New York, N. Y., a corporation of DelawareApplication January 18,1937, Serial No. 121,182

.4 Claims.

This invention relates to certain new and useful improvements in agrinding and classifying apparatus, and more particularly to anapparatus of this character in which the materialrejected 5 by theclassiiyingor separating portion of the apparatus is returned to thegrindingmechanism for further treatment.

In apparatus of the above character, it is customary to cause a streamof air to fiow through the pulyerizing chamber so as to carry the finelydivided material in suspension into the classifying or separatingchamber. The heavier particles of material, and to some extent portionsof the lighter material, are thrown out 01' the' main air stream eitherby the expansion and whirling movements of the air stream itself or bydirect contact with a revolving element of the classifer. Heretofore, asubstantial portion of the fine materialejected from the air stream hasbeen returned to the grinding pr pulverizing chamber of the millalongwith the heavier material; The fine material thus returned to thegrinding chamber not only interferes with the I grinding operation ofthe mill but also lowers the saturation of material in the air streamadjacent the classifier and thereby interferes with the emcientseparation or grading of the material.

The principal object of the present invention is to provide new andimproved mechanism which functions. to increase the grinding capacity ofapparatus of the above character without the use of additional powerand'which functions also to maintain the air stream heavily laden withpuiverized material in the zone of classification,

whereby the classifying or separating mechanism will be highly selectivein its function of determining the degree of fineness of materialdischarged from the apparatus.

A more specific object of the invention is to 40 provide, in apparatusof the above general character, means for intercepting the materialgravitating from the zone of classification and reintroducing saidgravitated material into the air stream whereby the lighter particles ofsuch ma- .45 terial will be again carried upwardly into the zone ofclassification and whereby the heavier particles of material will bepermitted to drop into the grinding chamber. Further objects andadvantages of the invention will be readily apparent from' the followingdetailed description of one approved form oi? apparatus constructed andoperating according to the principles of this invention.

In the accompanying drawings: 1

to I Fig. 1 is a vertical sectional view taken through blower orexhauster (not shown) connected some- (CI. 83-45) i the grinding andseparating'chambers of an apparatusconstructed in accordance with thisinvention.

Fig. 2 is a plan view of a cone element employed in the construction oiFig. 1 for intercepting ma- 5 terial .gravitating from the upper portionof the classifying chamber and i'orreturning it to the air stream sothat the lighter portions or the intercepted material will be againreturned to the classifier; and

Fig. 3 is a vertical section takenon line 1-3 0 Fig. 2. a

The apparatus herein shown may-be generally described as comprising apulverizing mill A, from which an air stream carrying pulverizedmaterial 15 in suspension is discharged through a conduit B, aclassifier C for determining the degree of fine-- ness of the materialto be discharged from the apparatus, and the improved means D adapted toreceive portions of the materir g avitati' from the classifier andreturn such 1..aterial to the air stream, whereby the finer portions ofthe material will be again carried into the zone' of classification,while the heavier particles of the intercepted material will bepermittedto return to the grinding mechanism for further treatment. It will beunderstood that the said air stream may be caused to flow through thegrinding and separating chambers of the mill by means of a suitablewhere in the system, usually in the conduit B and that the materialsuspended in the air stream and thereby discharged through the conduit Bmay be separated or removed from the air stream by means of any suitabledust collector.

The mill A and the classifier C of the present apparatus may be of anysuitable construction. For the purpose of convenience, the improvementsof the present invention are illustrated in connection with a mill and aclassifying mechanism of the type shown in the copending application ofRichard F. OMara, Serial No. 16,443, filed April 15, 1935, now PatentNo. 2,108,609.

The mill A comprises a vertically disposed cylindrical casing insupported on a suitable frame structure ii. A hearing member i2 extendsinto the grinding chamber of the mill and supports a vertical shaft i3.The shaftis operated by means of a bevel gear i l mounted on its lowerportion and meshing with a pinion IS on a horizontal shaft iii, thelatter of which may be driven by any suitable source'of power. A spidermember ll-securedto the upper end of the shaft 13 is.provided withradially extending arms l8 adapted to support a circular series ofroller-carriers l9, each pivoted at 20 to one of the spider arms I! sothat the grinding rollers 2| supported on the carriers IQ for freerotation may swing radially toward andfrom the shaft I3. When thevertical shaft I3 is rotated the rollers 2| swing outwardly under theinfluence of centrifugal force and bear against a bull-ring 22. Thematerial to be pulverized is fed into the mill by means of a pocketfeeder 23 rotatably mounted in a chute 24, the latter of whichcommunicates with the grinding chamber at a location above the rollers2| and bull-ring 22. In order to pick up material which may fall belowthe rollers 2| a suitable plow structure 24 is carried by a vertically arotary deflecting means D is positioned in the path of the air stream.This means is in the form of a cone-shaped member 21 which is preferablysecured to the upper end of the shaft l3 so as to rotate therewith aboutthe vertical axis ofthe grinding mechanism. It will be understood,however, that the member 21 can, if desired. be rotated by'a separatemechanism without departing from the principles of the presentinvention. Preferably the cone is made up of a central sheet 28 and aplurality of semi-circular intermediate and outer sheets 29-40. The edgeportions of the sheets 29 and 30 are secured together in abuttingrelation by means of butt strips 3l-32 so as to provide relativelysmooth inner and outer surfaces to the cone shaped member. The centersheet 28 is secured to the intermediate sheets 2929 and to a hub member33 which is slotted to receive a portion of the key 34 and therebysecure the hub rigidly to the shaft l3; The hub is held to the shaftagainst upward movement by means of a bolt which passes through thecentral disk 35 and into the upper end of the shaft l3. The said disk.35 preferably is brazed or suitably welded to the center sheet 28substantially as shown in Figs-3 of the drawings. 7

The upwardly moving air stream impinges against the bottom of the cone21, the coarser particles being returned to the grinding mechanism, andthe air stream with the fined material suspended therein being deflectedoutwardly so as to pass around the outer edges of the cone and into theclassifier C. 60

The classifier, of the present embodiment of the invention, is arrangedabove and in direct communication with the grindingchamber of the mill.The classifier chamber consists, preferably, of a casing having aconical portion 31, an upper cylindrical portion 38 and a top cover 39.The discharge conduit Bis preferably arranged to communicate through thecentral portion of the plate 39 at a'location above a revoluble'classifying mechanism designated generally by the reference numeral 40.Gear casing 4| is supported centrally within the downwardly and inwardlytapered portion 31 of the classifier by means of radially extendingsupporting plates 42, the said plates 42 being arranged edgewise to themovement of the air stream so as to provide as little resistance aspossible. A vertical shaft 43 extends upwardly from the gearcasing 4|and supports a revoluble deflector or whizrer 44. This member preferablycomprises a closed central portion 45 and a plurality of radiallyprojecting vanes or blades 46. The outer ends of these blades arebeveled inwardly and upwardly as indicated at 41. and rotate in closeproximity to the lower surface of a downwardly and outwardly projectingannular conical deflector secured to the inner wall of the cylindricalportion of the classifier housing. The deflector member and shaft 43 areoperatively connected to a horizontally extending shaft 49 by means ofsuitable gearing arranged in the gear casing 4|. The shaft 49 may bedriven by any suitable source of power, for example, a variable speedmotor E. It is customary, in classifiers of the type herein shown, tovary the speed of the deflector mechanism in accordance with the gradeor degree of fineness of material desired. The operation of thedeflector or separator, it has been discovered,

,is moreselective as to the number of grades of material discharged whenthe air stream is heavily laden with material in the zone ofclassification. This desirable condition is maintained in the presentimproved apparatus by means of the rotating cone member 21. The heavierparticles of material and a portion of the sufficiently pulverizedmaterial are ejected from the air by the expansion and whirlingmovements of the air after it passes through the restricted passage 56between the cone and the wall of the grinding chamber. Furtherquantities of material are rejected and thrown out of the air stream bydirect contact withthe deflector blades 46 of the classifier mechanism.A portion of the material, particularly the heavier particles thereof,may return directly to the mill through the space 50. However, a largeportion of the material gravitating from the zone of classificationtoward the grinding chamber is intercepted by the cone 2'! and thrownoutwardly by the rotation of the cone into the path of the air stream,whereby the lighter particles of the material are added to the dustladen air from the grinding chamber and carried upwardly toward therotating deflector 40. The heavier particles of intercepted materialthrown outwardly by the rotation of the cone 21 will drop through theopening 50 into the grinding chamber wherein they are further pulverizedby the rollers 2|.

By intercepting the rejected material in the manner above described, thematerial returned to the grinding chamber is confined largely to theheavier particles or tailings. The finer particles of material, whichmight otherwise reenter the grinding chamber and interfere with thegrinding operation, are reintroduced into the air stream at a locationabove the grinding mechanism so as to increase the saturation of finermaterial in the air immediately below the rotatin'g deflector 49. Asthesaturation of dust in the air above the revolving cone increases, theair will drop the heavier of these particles of material which are toofine to otherwise return to the grinding zone and are too coarse tobedischarged with the finished product. Eventually a state of balance willbe reached whereby additional oversized material passing into theclassifying chamber will be returned to the grinding zone withoutreturning an appreciable amount of material which has been sumcientlypulverized.

I c aim:

1. A grinding and classifyihg'apparatus comprising a casing, grindingmechanism includinga vertically disposed shaft in the lower portion ofthe casing, an air inlet in the lower portion of the casing, an outletin the upper portion of the casing for the discharge of pulverizedmaterial in suspension in the air moving upwardly through the casing, a'revoluble deflector in the upper portion of the casing for ejecting theheavier portionsof material from the air stream, whereby the ejectedmaterial gravitates toward the lower portion of the casing, and arevoluble inverted cone element centrally fixed to the vertical shaft ofthe grinding mechanism for intercepting and returning upwardly andoutwardly into said air stream portions of material gravitating from theupper part of the casing. a

2. A grinding and classifying apparatus comprising a casing having avertically disposed cylindrical grinding chamber and a classifyingchamber communicating with the grinding chamber, grinding mechanism inthe grinding chamber including a vertically'disposed shaft and acircular series of roller elements swingably supported thereon to rotateabout a vertical axis,

means for feeding material into the grinding chamber, an inlet foradmission of an air stream v to the grinding chamber, an outlet conduitleading from the upper portion of the classifying chamber for thedischarge of pulverized material suspended in said air stream, aclassifier in the upper portion of the classifyingchamber comprising arevoluble deflector having a closed central portion and a plurality ofradially extending deflector blades adapted to eject the heavierpartitles of material from the air 'stream, whereby the said ejectedmaterial gravitates toward the grinding chamber, and means comprising aninverted cone member secured to the upper portion of said verticallyextending shaft at a location intermediate the grinding and classifyingmechanisms for intercepting the said gravitating material and returningit upwardly and outwardly,

under the influence of centrifugal force, to the said air stream wherebythe lighter particles thereof are again carried upwardly to theclassifying mechanism. a

3. A grinding and classifying apparatus comprising a casing, a grindingmechanism in the casing including a vertically disposed shaft and acircular series of roller elements supported thereon to rotate about avertical axis, an inlet for the admission of an air-stream to the lowerportion of the casing, an outlet conduit leading from the upper portionof the casing for the discharge of pulverized material suspended in saidair stream, a classifier in the upper portion of the casing comprisingan outer annular stationary deflector member, and a revoluble deflectorassociated therewith and comprising deflector blades with openingstherebetween for the passage of the air stream, and means formaintaining the air stream heavily laden with finely divided materialcomprising a revoluble inverted cone member mounted on'the verticallydisposed shaft to rotate about a vertical axis at a locationintermediate the grinding mechanism and said 10 classifying mechanismand positioned in the path of the air stream, whereby the air streamimpinging against the lower surface of the cone member is deflectedoutwardly to pass around the outer edges of the cone and wherebymaterial ejected from said air stream above the cone shaped member iscollected on the upper surface of the cone and delivered by theinfluence of centrifugal force upwardly and outwardly into the airstream, whereby the heavier particles of so such material are returnedto the grinding chamber and the lighter particles are carried upwardlytoward the classifying mechanism.

4. A grinding and Sen -t lting ap aratus comprisinga casing providedwith a grinding cham- 25 ber and having an inlet in its lower portionfor an air stream and a separating chamber positioned above and indirect communication with the grinding chamber, the air stream carryingpulverized material upwardly in suspension from 30 the grinding chamberto the separating chamber, a grinding mechanism in the grinding chamber,a revoluble deflector in the separating chamber for rejecting andreturning downwardly toward the grinding chamber the heavier portions ofmaas terial from'the air stream, an outlet in the upper portion of thechamber for the discharge of pulverized material in suspension in theair stream,

and a revoluble inverted conical member pivoted centrally between thegrinding and separating 4 chambers to rotate about a vertical axis withits periphery spaced from the casing wall to provide an annular space,the cone serving as a deflector to force the air stream to flow upwardlythrough the annular space adjacent the casing wall, a

and the upper surface of the cone serving as ,a receptacle forcollecting materials gravitating downwardly from the separatingchamber'and returning these materials outwardly and upwardly by.centrifugal force into the upwardly w flowing air stream, whereby thelighter particles of this material may be again carried upwardly by thesaid air stream, and the heavier particles may gravitate downwardlythrough the annular space into the grinding chamber.

JOE CRI'I'ES.

